import { useEffect, useRef, useState } from "react";
import {
  catchUpDays,
  CATCH_UP_DAYS,
  dailiesId,
  dayKey,
  msUntilReset,
  streakOf,
} from "../../shared/daily.ts";
import { useGameMeta } from "../state/gameMeta.tsx";
import { isCustomGameId, type DisplayEvent, type LaneId } from "../../shared/custom.ts";
import type { GameMeta } from "../../shared/games.ts";
import type { GameId, Region } from "../../shared/schema.ts";
import { formatRemaining } from "../../shared/time.ts";
import { DayPip } from "./DayPip.tsx";
import { Fireworks } from "./Fireworks.tsx";

/**
 * The chores no source publishes.
 *
 * Commissions, sanity, daily training — the routine that runs whether or not
 * an event is on. They are the most-missed thing in every one of these games
 * and they appear on no wiki page, so they are a fixed client-side list rather
 * than feed data. Ticking one is stored in exactly the same day log an event's
 * checklist uses, so streaks and exports work the same way for both.
 *
 * Running events that repeat sit here too, so ticking today off never means
 * opening a sheet to find the checklist. The checklist is still where the whole
 * run lives — this is just today's line of it.
 *
 * Sits above the event list because it is the one part of the page that is
 * answerable in ten seconds and expires tonight.
 */

/** One thing to tick: a game's standing chore, or one of its repeating events. */
export interface DailyItem {
  /** The day-log key — `dailies:<game>` for a chore, the event id otherwise. */
  key: string;
  game: LaneId;
  label: string;
  title: string;
  ariaLabel: string;
  today: string;
  resetsIn: number;
  /**
   * Where a catch-up strip starts: the event's start, or null for a chore,
   * which has no start because it is a routine rather than an event.
   */
  notBefore: number | null;
}

/** A game and everything of its that wants ticking today. */
export interface DailyGroup {
  game: LaneId;
  meta: GameMeta;
  items: DailyItem[];
}

/**
 * A game's dailies, together.
 *
 * This used to be `[...chores, ...repeating]` — every game's standing chore,
 * then every repeating event — which put Genshin's commissions and Genshin's
 * login event at opposite ends of the strip with a dozen other games between
 * them. The reader thinks in games: if they marked an event as repeating, it
 * belongs beside the chores of the game it came from.
 *
 * The chore comes first inside a group because it is the one that exists every
 * day; the events follow **in the order they arrived**, because grouping is not
 * a licence to re-sort within a group — the same rule `lanes.ts` states for the
 * timeline's lanes.
 *
 * A lane the reader invented contributes events but no chore: there is no
 * routine we could name on their behalf (`docs/DATA-MODEL.md` § Reader-authored
 * key spaces). A group with nothing in it is dropped rather than rendered as an
 * empty heading.
 *
 * Pure, and exported so it is tested directly — the pattern `Timeline.tsx` uses
 * for `boardWindow` and `splitAt`.
 */
export function dailyGroups(
  games: readonly LaneId[],
  events: readonly DisplayEvent[],
  now: number,
  region: Region,
  meta: (id: LaneId) => GameMeta,
  startOf: (event: DisplayEvent) => number,
): DailyGroup[] {
  // A lane can arrive through an event without being in `games` — an event on a
  // game the reader has since switched off, say — and dropping it here would
  // quietly remove a tickable line. Ordered lanes first, then any straggler in
  // the order its events came.
  const lanes: LaneId[] = [...games];
  for (const event of events) {
    if (!lanes.includes(event.game)) lanes.push(event.game);
  }

  const groups: DailyGroup[] = [];
  for (const lane of lanes) {
    const game = meta(lane);
    const items: DailyItem[] = [];
    const today = dayKey(now, region, lane);
    const resetsIn = msUntilReset(now, region, lane);

    if (!isCustomGameId(lane)) {
      items.push({
        key: dailiesId(lane as GameId),
        game: lane,
        label: game.short,
        title: game.dailyTasks,
        ariaLabel: `${game.name} dailies — ${game.dailyTasks}`,
        today,
        resetsIn,
        notBefore: null,
      });
    }

    for (const event of events) {
      if (event.game !== lane) continue;
      items.push({
        key: event.id,
        game: lane,
        label: event.title,
        title: `${game.name} — ${event.title}`,
        ariaLabel: `${event.title} (${game.name})`,
        today,
        resetsIn,
        notBefore: startOf(event),
      });
    }

    if (items.length > 0) groups.push({ game: lane, meta: game, items });
  }
  return groups;
}

export function Dailies({
  games,
  events,
  region,
  now,
  daysFor,
  onToggleDay,
}: {
  /** Every lane the reader is looking at, in their own order. */
  games: LaneId[];
  /**
   * Live events that repeat daily — detected, or marked by the reader — and
   * that the reader has not already finished or ignored. An event they marked
   * done has no line left to tick, and listing it is the app arguing with them.
   */
  events: DisplayEvent[];
  region: Region;
  now: number;
  daysFor: (id: string) => string[];
  onToggleDay: (id: string, day: string) => void;
}) {
  const gameMeta = useGameMeta();
  /**
   * Whether the strip is showing the last fortnight.
   *
   * Per-visit state and deliberately not a stored preference, for the reason
   * expanding a truncated list is not one: it is something a reader does while
   * reading — "I did Tuesday, let me say so" — rather than a statement about how
   * the app should work.
   */
  const [catchUp, setCatchUp] = useState(false);

  // Each game rolls on its own server clock, so "today" is asked per game
  // rather than once for the section — Endfield's European day can still be
  // yesterday's while every HoYo game has already turned over.
  const groups = dailyGroups(
    games,
    events,
    now,
    region,
    gameMeta,
    (event) => Date.parse(event.startsAt),
  );
  const items = groups.flatMap((group) => group.items);
  const total = items.length;
  const complete = items.filter((i) => daysFor(i.key).includes(i.today)).length;
  const allDone = total > 0 && complete === total;

  const [burst, setBurst] = useState(0);
  // Null until the first render has been seen, so arriving at a page where
  // everything is already ticked is not treated as having just finished it.
  const previous = useRef<{ total: number; complete: number } | null>(null);

  useEffect(() => {
    const was = previous.current;
    previous.current = { total, complete };
    if (was === null || !allDone) return;
    // Celebrate finishing the last one, and only that. The list also gets
    // shorter when the reader focuses a single game or marks a repeating event
    // done, which can land on "all complete" without them having ticked
    // anything — a burst there is the app congratulating them for filtering.
    // Backfilling a past day moves no count here, so it never bursts.
    if (was.total === total && complete > was.complete) setBurst((n) => n + 1);
  }, [total, complete, allDone]);

  useEffect(() => {
    if (burst === 0) return;
    const id = setTimeout(() => setBurst(0), 1400);
    return () => clearTimeout(id);
  }, [burst]);

  if (total === 0) return null;

  // With mixed reset clocks there is no single "resets in", so the header
  // reports the next one to land and says that it is the next one.
  const soonest = Math.min(...items.map((i) => i.resetsIn));
  const mixed = new Set(items.map((i) => i.resetsIn)).size > 1;

  return (
    <section className="relative border-b border-hairline px-4 py-4">
      {burst > 0 && <Fireworks key={burst} />}

      <div className="relative flex items-baseline justify-between gap-3">
        <h2 className="eyebrow">
          Today's dailies · {complete}/{total}
        </h2>
        <p className="tnum text-[0.6875rem] text-faint">
          {mixed ? "next reset in " : "resets in "}
          {formatRemaining(soonest)}
        </p>
      </div>

      {catchUp ? (
        <CatchUpPanel
          groups={groups}
          now={now}
          region={region}
          daysFor={daysFor}
          onToggleDay={onToggleDay}
        />
      ) : (
        /* One wrapping row, with each game's chore and its events adjacent. No
           per-game headings here: this is the part of the page answerable in ten
           seconds, and a heading per game would make it the tallest block on it,
           pushing "next to expire" — the answer the reader came for — down the
           page. The hue already says which game a chip belongs to. */
        <ul className="relative mt-2.5 flex flex-wrap gap-1.5">
          {items.map((item) => (
            <li key={item.key}>
              <TickChip
                label={item.label}
                hue={gameMeta(item.game).hue}
                title={item.title}
                ariaLabel={item.ariaLabel}
                days={daysFor(item.key)}
                today={item.today}
                onToggle={() => onToggleDay(item.key, item.today)}
              />
            </li>
          ))}
        </ul>
      )}

      <div className="relative mt-2 flex items-baseline justify-between gap-3">
        <p className="text-[0.6875rem] leading-relaxed text-faint">
          {catchUp
            ? `Tick a day you did but didn't record. The last ${CATCH_UP_DAYS} days, and nothing later than today.`
            : allDone
              ? "All done. Nothing else expires tonight."
              : `${waiting(total - complete)} still waiting on you today.`}
        </p>
        {/* The way back to a day you already did. It lives on the section rather
            than on each chip because a chip is a single tick target, and a
            second control inside one is a mis-tap that costs a streak. */}
        <button
          type="button"
          onClick={() => setCatchUp((on) => !on)}
          aria-expanded={catchUp}
          className="shrink-0 text-[0.6875rem] text-faint transition-colors hover:text-muted"
        >
          {catchUp ? "Done" : "Catch up"}
        </button>
      </div>
    </section>
  );
}

/**
 * The last fortnight, for saying you did a day you never ticked.
 *
 * Its own component rather than a branch inside the section, so it can be
 * rendered and asserted on directly — the interesting parts are which days
 * appear and whose clock they were cut on, and neither is reachable through a
 * `useState` from a test.
 *
 * Expanded there is vertical room, so the grouping becomes a heading per game.
 * Collapsed it is adjacency alone: the strip is the part of the page answerable
 * in ten seconds, and a heading per game would make it the tallest block on it.
 *
 * Every strip is cut with its own item's game, never the section's — Endfield
 * serves Europe off the Americas machine, so a tick written under one clock and
 * read under another is a day the reader loses.
 */
export function CatchUpPanel({
  groups,
  now,
  region,
  daysFor,
  onToggleDay,
}: {
  groups: DailyGroup[];
  now: number;
  region: Region;
  daysFor: (id: string) => string[];
  onToggleDay: (id: string, day: string) => void;
}) {
  return (
    <div className="relative mt-3 flex flex-col gap-3">
      {groups.map((group) => (
        <div key={group.game}>
          <p
            className="text-[0.6875rem] font-semibold"
            style={{ color: group.meta.hue }}
          >
            {group.meta.name}
          </p>
          {group.items.map((item) => (
            <div key={item.key} className="mt-1.5">
              <p className="truncate text-xs text-muted">{item.label}</p>
              <div className="mt-1 flex flex-wrap gap-1">
                {catchUpDays(now, region, item.game, item.notBefore).map((day) => (
                  <DayPip
                    key={day}
                    day={day}
                    today={item.today}
                    done={daysFor(item.key).includes(day)}
                    onToggle={() => onToggleDay(item.key, day)}
                  />
                ))}
              </div>
            </div>
          ))}
        </div>
      ))}
    </div>
  );
}

/**
 * One thing to tick off today.
 *
 * The same pill whether it is a game's standing chore or an event that repeats:
 * to the reader at 23:50 they are the same job, and the distinction between
 * "the app knows about this" and "a wiki published it" is ours, not theirs.
 *
 * The game's hue is on the border in both states — faintly while the job is
 * outstanding, fully once it is done. A chip that only takes its colour on
 * completion means the strip you actually scan, the unfinished one, is a row of
 * identical grey pills with no clue which game each belongs to.
 *
 * The outstanding tint is kept low enough to read as a hint rather than a
 * state: it has to say *which game* without competing with the tick, which is
 * the only thing on the chip that answers the question the reader came with.
 * Ticking one should be a visible jump, not a nudge.
 */
function TickChip({
  label,
  hue,
  title,
  ariaLabel,
  days,
  today,
  onToggle,
}: {
  label: string;
  hue: string;
  title: string;
  ariaLabel: string;
  days: string[];
  today: string;
  onToggle: () => void;
}) {
  const isDone = days.includes(today);
  const streak = streakOf(days, today);

  return (
    <button
      type="button"
      onClick={onToggle}
      aria-pressed={isDone}
      aria-label={`${ariaLabel}${isDone ? ", done today" : ", not done today"}`}
      title={title}
      // `.hue-chip` is the shared hover: the chip's own colours are the game's
      // hue and arrive inline, which no rule can override, so it is drawn from
      // what inline does not own. `--hue` below is the only thing it needs;
      // pressed-ness it reads off `aria-pressed`, which is already up there.
      className="hue-chip flex max-w-[15rem] items-center gap-2 rounded-full border px-3 py-1.5 text-xs font-medium"
      style={{
        ["--hue" as string]: hue,
        borderColor: isDone ? hue : `color-mix(in srgb, ${hue} 20%, transparent)`,
        // Colour identifies the game; done-ness is carried by the tick, the
        // full-strength border and the wash. Keeping the label readable matters
        // more than saturating it, so an outstanding chip stays on muted ink.
        color: isDone ? hue : "var(--color-muted)",
        background: isDone
          ? `color-mix(in srgb, ${hue} 14%, transparent)`
          : `color-mix(in srgb, ${hue} 3%, transparent)`,
      }}
    >
      <svg viewBox="0 0 16 16" aria-hidden className="size-3 shrink-0">
        <path
          d="M2.5 8.5l3.5 3.5 7.5-8"
          fill="none"
          stroke={isDone ? "currentColor" : hue}
          strokeWidth="2.2"
          strokeLinecap="round"
          strokeLinejoin="round"
          opacity={isDone ? 1 : 0.25}
        />
      </svg>
      <span className="hue-chip-label truncate">{label}</span>
      {streak > 1 && (
        <span className="tnum shrink-0 text-[0.625rem] opacity-70">{streak}d</span>
      )}
    </button>
  );
}

function waiting(n: number): string {
  return n === 1 ? "One thing" : `${n} things`;
}